The invention relates to card punching data recording devices, more specifically punch card voting devices, which are adapted to operate upon tabulating cards of the kind in which the index-point area of each card are individually scored to provide selectively removable "chips" or punchouts commonly referred to as "chad."
Devices of this kind are disclosed in Harris U.S. Pat. Nos. 3,201,038 and 3,240,409. In such data recording devices, the instrument employed to remove the card material does not have a cutting or shearing action in the manner of an ordinary punch. Rather, it functions merely to apply to a selected chip sufficient force to break the frangible connections between that chip and the card, thereby detaching the chip from the card. The expressions "punch" and "punching," as employed herein, should be understood to have this meaning. Similarly, reference made herein to a "die" should not be construed as meaning a die of the kind in which a shearing action takes place.
Card punching devices of the aforesaid type commonly include a punch board or die comprising parallel strips of thin, resilient material that are adapted to provide a firm support for the main body of the card and to yield wherever necessary to permit the passage of a chip of card material as the same is pushed out of the card and between adjacent strips by the punching tool. When such a punch board or die is utilized, precautions must be taken to insure that all of the chips punched from the card are expelled from between the resilient die strips and that none of these chips will remain caught in the grip of the tightly spaced resilient strips after the punching tool is withdrawn. If chips are permitted to accumulate between the resilient strips, this can interfere with the punching operations, and occasionally it has been observed that a partially punched chip has been left clinging to a card after the punch was withdrawn, because the card-supporting surface of the punch board had become so clogged with chips as to prevent a clean punching operation. Incompletely punched cards can cause serious errors to occur in data processing operations utilizing such cards.
In punch card voting devices, a template has been used to guide the voter's punch or stylus onto the selected punch position. If, however, the voter does not hold the voting punch straight up and down when punching, it is possible under certain temperature and humidity conditions to pull the template toward the voter a few thousandths of an inch, sufficient to prevent complete removal of the chad when the stylus is inserted. This can produce what is called a "hanging chad," as the chad-piece of the card is still attached to the card by one or two of the frangible holding points.
Through analysis and experience, it has been found that the construction of the punch boards is principally responsible for these problems. It must be emphasized that the presence of even one incompletely punched chip in a run of several thousand tabulating cards is in most cases too great a defect to be tolerated. Hence, the design of the punch board becomes a critical and important factor in the successful use of prescored tabulating cards.
Punch boards which have been in use in punch card voting have employed a highly heat-sensitive material, ABS plastic, which causes the card, template, and template stops or abutments of the punch board to move away from their ideal registration location as the temperature rises or falls. Specifically, the template stops of the punch-bed, or punch frame as it is called in punch card voting, should be within a 0.007 inch tolerance zone for proper operation of the punch card voting device. With the ABS plastic, as has been used, having an expansion characteristic which allows 0.0005 inch longitudinal growth or expansion over the length of the punch frame per degree Fahrenheit, it is easily seen that the critical dimensions are exceeded when 14.degree. F. variations from an average 72.degree. F. are exceeded in a polling place, i.e., over 86.degree. F. or under 58.degree. F. Temperatures over 86.degree. F. or under 58.degree. F. may be found in garages, gymnasiums, halls, etc., which are used as polling places. Therefore, the material typically used for punch boards in punch card voting can and does contribute to potentially unreadable votes, because of hanging chad or mispunched cards.
As previously constructed, punch card data recording devices were difficult or impossible to dismantle for removal and replacement of the resilient die strips, or costly assemblies were employed to enable such dismantling. There has been a need for a simple, inexpensive system of assembly which permits easy, nondesctructive separation of components, particularly in the connection of the lower card guide with the punch card frame body.
Another shortcoming of prior punch card recording devices has been the requirement of milling or machining the template and card positioning stops or abutments of the punch frame. The card positioning stops were molded into the plastic punch frame to limit the travel of the template and card as the card barely slips over the pins at the top or head end of the punch frame. The distance between the pins and the stops is quite critical and must be precisely controlled. However, because of the tolerance build-up and difficulty in repeat molding each part and assembling all together within a few thousandths of an inch tolerance, it was found that an expedient way to correct the inaccuracies of molding and assembly was to machine the distance from the pins to the template stops in order to obtain the correct dimension. Machining was performed on the stops after assembly. This has been necessary because of the method of assembly and the materials used. Methods of assembly have typically used solvent bonding, which melts some of the material of parts to be joined, then, when the solvent evaporates, leaves the parts joined together. Obviously, a machining operation is costly, and there has been a need for a simplified means of obtaining accurate spacing from the pins to the stops, without post-assembly machining.
Another defect of prior art punch frames has been that in order to retain the template in the device in its proper position during and between uses, a template retaining clip has been employed. The clips have often been installed improperly and have interfered with the template, causing the voting device to malfunction.